1. Field of the Invention
The present invention generally relates to a method of fabricating a semiconductor device, and more specifically, it relates to a method of fabricating a semiconductor device improved to be capable of attaining high reliability in junction between a plug part and a wire part. The present invention also relates to a semiconductor device obtained by such a method.
2. Description of the Prior Art
FIG. 9 is a sectional view showing an ideally formed conventional dynamic random access memory.
A capacitor 11 is formed on a semiconductor substrate 50. A metal wire 5 and lower conductor films 6 are connected with each other through plugs 3 embedded in contact holes 10. The height of the capacitor 11 tends to increase due to high integration. Consequently, the contact holes 10 tend to increasingly deepen. The contact holes 10 are 0.3 xcexcm to 0.4 xcexcm in diameter, for example, and 1.5 xcexcm to 2 xcexcm in depth.
A fabrication process for a conventional semiconductor element such as the dynamic random access memory is described. In order to form contactors for the metal wire 5 and the lower conductor films 6 by the tungsten plugs 3 or the like, the contact holes 10 are first formed in an interlayer isolation film. Thereafter tungsten employed as the plug material is deposited and totally dryly etched back so that unnecessary tungsten part is removed, thereby forming the plugs 3. Thereafter the metal wire 5 is formed on the plugs 3 as such.
If the dynamic random access memory is not ideally formed as shown in FIG. 9 but any contact hole 10 is filled up with a plug material 2 as shown in FIG. 10, however, a cavity 20 may be defined in the plug material 2.
When the plug material 2 having such a cavity 20 is etched back, the cavity 20 remains in the plug 3 as shown in FIG. 11.
Referring to FIG. 12, when a portion located on such a cavity 20 is not covered with the metal wire 5, i.e., when coverage is defective, a chemical solution (e.g., an organic solvent) employed in a wet step (a development step, a resist removal step or the like) for forming the metal wire 5 may penetrate into the cavity 20 to corrode the plug 3. This problem remarkably arises when the metal wire 5 is misregistered.
The metal wire 5 and the plug 3 may not come into contact with each other due to such corrosion, leading to reduction of reliability of wiring. Further, the plug 3 may dissolve in the chemical solution and disappear, to reduce reliability of wiring.
The present invention has been proposed in order to solve the aforementioned problems, and an object thereof is to provide a method of fabricating a semiconductor device improved to be capable of attaining excellent contact between a metal wire and a plug thereby improving reliability of wiring.
Another object of the present invention is to provide a method of fabricating a semiconductor device improved to cause no disappearance of a plug.
Still another object of the present invention is to provide a semiconductor device improved in reliability of wiring, obtained by such a method.
In the method of fabricating a semiconductor device according to the present invention, an interlayer isolation film is first formed on a semiconductor substrate. A contact hole is formed in the aforementioned interlayer isolation film. A plug material is formed on the aforementioned semiconductor substrate to fill up the aforementioned contact hole. The aforementioned plug material is etched back thereby forming a plug in the aforementioned contact hole. The surface of a cavity defined in the aforementioned plug is covered with an insulator film. A metal wire is formed on the aforementioned interlayer isolation film to be in contact with the aforementioned plug.
According to a preferred mode of the present invention, the step of covering the surface of the cavity defined in the aforementioned plug with the insulator film includes a step of completely filling up the cavity formed in the aforementioned plug with the insulator film.
Alternatively, the step of covering the surface of the cavity defined in the aforementioned plug with the insulator film includes a step of covering the surface of the cavity without completely filling up the cavity formed in the aforementioned plug with the aforementioned insulator film.
The aforementioned insulator film preferably includes an SiN film.
This method is preferably applied to a method of fabricating a dynamic random access memory.
A semiconductor device according to another aspect of the present invention comprises a semiconductor substrate. An interlayer isolation film is formed on the aforementioned semiconductor substrate. A contact hole is formed in the aforementioned interlayer isolation film. A plug is formed in the aforementioned contact hole. The surface of a cavity defined in the aforementioned plug is covered with an insulator film. A metal wire is provided on the aforementioned interlayer isolation film to be in contact with the aforementioned plug.
According to a preferred mode of the present invention, the aforementioned insulator film completely fills up the aforementioned cavity.
According to another preferred mode of the present invention, the aforementioned insulator film does not completely fill up the aforementioned cavity
The aforementioned insulator film preferably includes an SiN film.
This semiconductor device includes a dynamic random access memory.